As with so many other things, there’s a right way and a wrong way to create custom attributes for use with Exchange. These attributes can be made to appear in the custom attribute slots in Outlook, so you can extend the GAL (and views of it) to include things like birthdays, employee IDs, or other data not include in the schema. The wrong way is just to pick what looks like an unused MAPI attribute ID. Dave Goldman explains the right way here.
Technorati Tags: Exchange 2007